What Is ALD? Understanding Adrenoleukodystrophy

What causes ALD?

ALD is caused by disease-causing changes in a gene called ABCD1. This gene provides instructions for a protein involved in processing certain fats called very long-chain fatty acids, or VLCFAs. When the protein does not work properly, these fats can build up.

You may see ABCD1 and VLCFA on a genetic or blood-test report. They describe different pieces of information. Not every change found in ABCD1 is known to cause disease, and a blood-test number needs clinical interpretation.

Sources: MedlinePlus Genetics: ALD · MedlinePlus: interpreting genetic results.

What parts of the body can ALD affect?

ALD can affect several parts of health. These can overlap, but they are not a sequence that everyone goes through.

Brain: cerebral ALD

Inflammation and damage to myelin, the protective covering around nerve fibers in the brain, can affect learning, behavior, vision, movement, and other abilities. Cerebral ALD can occur in childhood or adulthood. Read about cerebral ALD and MRI monitoring.

Adrenal glands

The adrenal glands may not make enough of certain hormones, including cortisol. This is called adrenal insufficiency and needs its own assessment and care. It does not by itself mean someone has cerebral ALD. Read about adrenal health.

Spinal cord and nerves

Myeloneuropathy can involve leg stiffness or weakness, walking difficulties, pain, and bladder or bowel concerns. In men with ALD, this pattern is often called adrenomyeloneuropathy, or AMN. Women can develop similar neurological symptoms. Read about AMN and women’s own health.

Some people have no noticeable symptoms when ALD is identified. A diagnosis does not tell you which problems a person will develop or when. Another relative’s experience cannot predict an individual’s course.

Sources: MedlinePlus Genetics · International ALD recommendations, 2022.

What symptoms should we ask about?

New changes in attention or learning, behavior, speech, vision, walking, or coordination deserve a conversation with the care team. Ongoing leg stiffness, weakness, or bladder and bowel problems are also worth discussing.

Adrenal symptoms can include unusual tiredness, poor appetite, weight loss, or changes in skin color. These symptoms can have other causes; a list cannot diagnose ALD or identify which part of ALD is involved.

If someone with ALD develops new or worsening concerns, contact the care team promptly rather than waiting for the next routine appointment. Ask which situations need urgent help. Our adrenal guide includes emergency information for suspected adrenal crisis.

Sources: MedlinePlus: signs and symptoms · International ALD recommendations.

How is ALD found and diagnosed?

Families may first hear about ALD through newborn screening, symptoms, or a relative’s diagnosis. Those starting points lead to different questions.

After newborn screening

An out-of-range screen means follow-up testing is needed. It does not by itself confirm ALD or predict a child’s future health. Follow-up may include blood tests and ABCD1 genetic testing, with a specialist explaining what the results mean together.

The newborn screening guide walks through follow-up and questions for the first appointments.

Sources: HRSA: newborn screening results and follow-up · International ALD recommendations.

After a genetic test

A known disease-causing ABCD1 variant can confirm ALD. A variant of uncertain significance, or VUS, is different: there is not enough evidence to classify the change as disease-causing or benign. A VUS alone does not establish or rule out a diagnosis, and it should not be assumed harmless.

Ask which findings support the diagnosis, what is still uncertain, and who will revisit the interpretation. Our Grey Zone guide explains uncertain results and the limits of current research.

Sources: International ALD recommendations · MedlinePlus: genetic test results.

Can adults and women have ALD?

Yes. ALD is not limited to children. Adults may be diagnosed because of symptoms, family testing, or a child’s newborn screening result.

Women with a disease-causing ABCD1 variant can develop neurological symptoms in adulthood. The word “carrier” is sometimes used when discussing inheritance, but it should not be taken to mean that women cannot be affected.

Cerebral ALD and adrenal insufficiency are extremely rare in women, and routine monitoring recommendations differ from those for boys and men. Women’s own symptoms and care needs still deserve attention. See our dedicated women with ALD guide and broader adult ALD and AMN guide.

Sources: MedlinePlus Genetics · International ALD recommendations.

How is ALD inherited?

ABCD1 is on the X chromosome. This is why ALD is described as X-linked.

• If a woman has a disease-causing ABCD1 variant on one of her X chromosomes, each pregnancy has a 50% chance of inheriting that variant.
• In the usual X-linked inheritance pattern, a father with the variant passes it to his daughters and not to his sons.

These are chances of inheriting a variant, not predictions about symptoms or severity. ALD can also occur through a new genetic change, so an absence of known family history does not rule it out.

Our ALD genetics and inheritance guide explains how variants can be passed down and what testing may mean for relatives.

A genetic counselor can explain the actual report, discuss which relatives may benefit from testing, and talk through reproductive questions if you want that information. An uncertain result needs its own explanation; do not apply disease-risk assumptions to a VUS.

Sources: MedlinePlus: X-linked inheritance · International ALD recommendations · MedlinePlus: uncertain results.

Why monitor someone who feels well?

Some changes can be detected before a person notices symptoms. Monitoring gives the care team information about what is happening now and whether a next step is needed.

Brain MRI, adrenal blood tests, and a neurological examination answer different questions. A reassuring result in one area does not replace follow-up in the others. The plan depends on age, sex, diagnosis, earlier findings, symptoms, and the team’s assessment.

For boys and men with confirmed ALD, brain and adrenal surveillance are important parts of care. Women’s routine recommendations differ. If the diagnosis is still uncertain, ask what the proposed plan is based on and how it will be reviewed.

Sources: International ALD recommendations.

How is ALD treated?

Care depends on the part of ALD involved. It may include hormone replacement for confirmed adrenal insufficiency, help with neurological symptoms and daily function, or specialist assessment of treatment options for cerebral disease.

Treatments have different goals and eligibility requirements. A treatment for cerebral ALD should not be assumed to address adrenal insufficiency or all spinal cord and nerve symptoms. Benefits, risks, and timing need to be discussed with an experienced ALD team.

Our treatment and research guide covers selected current approvals, safety information, and questions about clinical trials. Your team should confirm what applies in your situation and where you receive care.

Sources: International ALD recommendations: care goals.

Choose your next guide

You can take this one question at a time. Each guide goes deeper into a different part of the experience.

A newborn screening result

Understand follow-up testing and prepare for the first conversations.

Family genetics and inheritance

Understand ABCD1 results and inheritance, testing relatives, and questions for a genetic counselor.

An uncertain genetic result

Explore the ALD Grey Zone and ABCD1 VUS, including what research can and cannot tell us.

Brain monitoring

Learn about cerebral ALD and MRI, preparing for scans, and questions about results.

Hormones and adrenal care

Explore adrenal health, blood tests, and prescribed illness or emergency plans.

Spinal cord and nerve symptoms

Understand adrenomyeloneuropathy (AMN), follow-up, and practical symptom care.

Coordinating adult care

Plan adult care and support, including moving between clinics or from pediatric services.

Women’s own health

Explore women with ALD, symptoms, follow-up, and support that addresses your needs.

Treatments or studies

Understand treatment goals and research, eligibility, and questions to bring to specialists.

Family life and practical help

Find support for appointments, school, siblings, and uncertainty, along with ways to connect with other families.

Looking for an organization or community? Visit our ALD directory. You can also return to the full resource library.

Questions for your first ALD conversation

• Is ALD confirmed, or are we still clarifying the screening or genetic result?
• What do the findings tell us about health now, and what can they not predict?
• Which specialists should be involved, and who coordinates our care?
• Which monitoring applies to us, and what is the next step?
• Would genetic counseling or testing for relatives be helpful?
• Where can we find emotional or practical support?

Bring the reports you have and write down the questions that matter most to you. It is reasonable to ask for time to understand an unfamiliar term.

A few terms you may hear

ABCD1

The gene in which disease-causing changes lead to X-linked ALD.

VLCFA

Very long-chain fatty acids, a group of fats involved in ALD biology and biochemical testing.

Myelin

Protective material around nerve fibers that helps them carry signals.

Pathogenic variant

A genetic change classified as disease-causing. The classification does not predict an individual’s symptom timeline.

Surveillance

Planned checks over time, including when someone feels well.

Sources: MedlinePlus Genetics · MedlinePlus: genetic results · International ALD recommendations.

Sources and further reading

Sources checked November 8, 2026. Medical expert review is still pending. Current treatment details are covered in the separate treatment guide.

• MedlinePlus Genetics: X-linked adrenoleukodystrophy · ALD biology, manifestations, and inheritance.
• HRSA: newborn screening results and follow-up · General information about screening results and next steps.
• Engelen and colleagues: international ALD recommendations · Neurology, 2022; diagnosis, monitoring, and care principles.
• MedlinePlus Genetics: interpreting genetic test results · Uncertain results and the limits of genetic information.